Digital-human interfaces (e.g., user interfaces) that provide closer to real life experiences are desired as digital devices evolve. Writing and drawing with human hands are fundamental processes for experience and expression. Existing devices that use touch sensitive screens are not precise enough to reproduce such experience or expression with sufficient accuracy. For example, a typical line width of a pen or pencil is 0.5 mm, and no screen technology available today sufficiently reproduces the handwriting experience at a reasonable cost. Some commercially available digitizing systems utilize position-dependent two-dimensional dots that are detected by sensor in a pen such as that available from Anoto Group AB.
Devices such as capacitive or resistive touch screens provide both input (touch) and output (display) capabilities. A touch screen is formed by placing a transparent overlay proximate to the display surface. Such overlays typically detect input (i.e., a “touch”) based upon a change in electrical properties of the overlay. The accuracy and resolution of these overlays is typically insufficient for precision writing, drawing, marking, etc., to provide a rewarding user experience. Existing systems that do provide the expected level of accuracy and resolution in touch (hand or writing instrument) frequently require unacceptably high background in the visual perception.
Other existing devices utilize a pen that includes a radiation source and a camera, to be used on visual devices such as display or screen for human-digital interface. These pens rely on tiny ink dots on the surface of the display. These ink dots, which are not transparent, block light from the underlying display and in effect, degrade the intensity of the display. Other existing devices rely on photo luminescent marks disposed on a surface; however, the intensity of fluorescence is not sufficient for a practical device. Other existing devices that use reflection (specular reflection) are not useful for handwriting applications because the angle of incidence needs to be nearly the same as the angle of reflection for the pen to detect the marks.